DE3418261C2 - - Google Patents

Description

The invention relates to a valve arrangement for control and Monitoring the working pressure of a hydraulic consumer the genus of the main claim.

It is already such a valve arrangement for control and Monitoring the working pressure of a hydraulic consumer e.g. B. the tailstock or the chuck of a machine tool known from DE 32 32 536 A1. This is controlled by a pilot Control oil flow flowing through a pressure reducing valve Flow indicator headed when falling below a given working pressure an electrical signal to switch off one machine delivers. With this valve arrangement you can use of the proportional pilot valve different Working pressures can be set, with no additional Adjustment processes on the flow indicator are necessary, which means a relatively high ease of use is achieved. A disadvantage of this valve arrangement, however, is that it works with a particular Working pressure, the amount of which works for the Clamping force setting as well as decisive for clamping pressure control is. Is used in this valve arrangement for clamping The flow indicator switches below the working pressure Machine off. In many hydraulic systems, e.g. B. by a Control of additional consumer pressure fluctuations in the Hydraulic system occur, which is a safe clamping process  not endanger, but with this valve arrangement an undesired Shut down the machine. It is therefore multiple desires that the valve assembly have limited pressure fluctuations processed without switching off the machine, which is only possible with Falling below a predetermined signal pressure for Tension control should happen. The one from the pressure reducing valve certain clamping pressure should limit the clamping force setting thereby by a predetermined pressure difference of a few bar above the Signal pressure for clamping pressure control.

The object of the invention is to provide a valve arrangement for control and Monitoring the working pressure of a hydraulic consumer as simple as possible to train that switching off a Machine control of the working pressure effective as clamping pressure is more independent, with print settings relatively easy should be feasible.

This task is solved by a generic Valve arrangement with the characteristic features of the Main claim. This has the advantage that the valve arrangement with an adjustable pressure difference between the higher clamping pressure and the lower control pressure works so that limited Pressure fluctuations in the hydraulic system do not become an undesirable Switch off the machine. The valve assembly builds relatively simple, preferably using existing components will. Only one has to be used to adjust the clamping pressure Adjusting element can be operated, the pressure difference being independent of the respective set value remains constant.

By the measures listed in the subclaims advantageous developments and improvements in the main claim specified valve arrangement possible. According to claims 2 and 3  the valve arrangement can be particularly simple and inexpensive produce. A construction according to the is also particularly advantageous Claims 4 to 7, whereby the pilot-operated pressure reducing valve on a particularly low clamping pressure is adjustable; in addition, the Pressure adjustment is unaffected by the pressure drop that caused a restriction in the flow indicator. Furthermore, the reduced throttle losses to save energy. Especially A training according to claim 8 is then advantageous, whereby at Use of a common proportional pilot valve for the Main stage of the pressure reducing valve is prevented in the event of failure the electrical control system the clamping pressure in an impermissible manner breaks down, so that a safety function is hereby achieved.

Several embodiments of the invention are in the Drawing shown and in the description below exercise explained in more detail. Show it

Fig. 1 shows a first Ven tilanordnung in a simplified representation,

Fig. 2 a corresponding pressure diagram,

Fig. 3 shows a part of a second embodiment of the valve arrangement and

Fig. 4 shows a longitudinal section through the double-pressure relief valve according to Fig. 3,

Fig. 5 shows a part of a third valve arrangement and

Fig. 6 shows a fourth Ventilanord voltage in a simplified representation with increased safety behavior.

The valve assembly 10 has an intermediate plate 11 and a 4/2-way valve 12 flanged thereon for directional control of a tensioning cylinder 13 serving as a hydraulic consumer.

In the intermediate plate 11 is an inlet channel 14 , which is supplied with pressure medium from a pressure network 15 with hydraulic accumulator 16 and throttle valve 17 . The inlet channel 14 is connected to the P-port 18 of the directional control valve 12 , during which the T-port 19 via a Rücklaufka channel 21 is relieved to a tank 22 .

The directional control valve 12 has an A connection 23 , which he connects to the working line 24 with a cylinder chamber 25 of the clamping cylinder 13 . One of the piston rod 26 in the cylinder 13 associated with the annular piston rod space 27 is connected via a second working line 28 to a B-connection 29 on the directional control valve 12 .

The spool of the directional control valve 12 is electromagnetic table in two switching positions and locked in them. It has a cross position 31 , in which it binds the inlet channel 14 to the piston rod chamber 27 and thus retracts the piston rod 26 when relaxing by extending the cylinder 13 to relax. In a parallel position 32 , the directional control valve 12 controls pressure medium in the cylinder chamber 25 , and the extending piston rod 26 carries out a tensioning process.

In the intermediate plate, a main stage 33 of a pilot-controlled pressure reducing valve 34 is connected in the inlet channel 14 , which limits the pressure in the P-connection 18 of the Wegeven valve 12 . A control connection 35 of the main stage 33 is connected to a first control line 36 , which is fed from a center connection 37 of a shuttle valve 38 and is led to the tank 22 . The two side connections of the shuttle valve 38 are connected to the first 24 and second working line 28 via a first 39 and second pressure line 41 .

In the control line 36 , a control throttle 42 and a pilot control unit 43 are connected in series downstream of the shuttle valve 38 . The control throttle 42 is arranged in the control line 36 so that the Druckab reached to the control connection 35 between it and the control unit 43 before and it can thus fulfill its task of piloting the main stage 33 .

The determining the clamping pressure in the cylinder chamber 25 before control unit 43 consists of two individual Drucksteuerein directions that are connected to each other in series in the first Steuerlei device 36 . In particular, these pressure control devices consist of an adjustable pressure limiting valve 44 and an upstream, adjustable pressure differential valve 45 . The adjustment of the two pressure valves 44 , 45 serving as pressure control devices can be carried out in any manner, for. B. mechanically or electrically. While the control pressure can be adjusted with the pressure relief valve 44 , the pressure difference valve 45 can preselect the pressure difference between the higher clamping pressure and the lower control pressure.

From the center connection 37 of the shuttle valve 38 , a second control line 46 leads in parallel to the first control line 36 to the pilot unit 43 . In the pilot unit 43 , the second control line 46 opens into the first control line 36 , specifically in a region between the two pressure valves 44 and 45 . In addition, a second throttle point 47 is connected in the second control line 46 .

Downstream of the pilot control unit 43 there is an orifice 48 in the first control line 36 , the back pressure of which acts on a hydroelectric pressure switch 49 . Diaphragm 48 and pressure switch 49 together form a flow indicator 51 .

The operation of the valve assembly 10 is explained as follows, reference being made to the diagram of FIG. 2, which shows a pressure curve in the cylinder chamber 25 over time.

It should be assumed that the 4/2-way valve 12 in its parallel position 32 pressure medium from the pressure network 15 and the hydraulic accumulator 16 controls the pressure reducing valve 34 in the cylinder chamber 25 , the piston rod 26 extending for the tensioning process. If the piston rod 26 has moved against the stop, the pressure between the throttle valve 17 for speed adjustment and the tensioning cylinder 13 increases . At the same time, the pressure in the cylinder chamber 25 is tapped via the first pressure line 39 and passes via the Wechselven valve 38 into the first control line 36 , where it acts on the control unit 43 and the main stage 33 of the pressure reducing valve.

It is now assumed that, according to the diagram in FIG. 2, the pressure in the cylinder space 25 runs up along the straight line 52 and reaches the pressure level p ₁ at time t ₁ . The pressure value p ₁ is the control pressure set with the pressure limiting valve 44 , when it is reached or exceeded the pressure limiting valve 44 opens and thus a small control oil flow via the second control line 46 with the throttle point 47 , the pressure limiting valve 44 and the first control line 36 flows to the tank 22 . The aperture 48 in the control oil flow generates a back pressure which actuates the pressure scarf ter 49, so that its electrical Ausgangssi gnal signals the attainment or exceeding of the control pressure in the cylinder chamber 25th After reaching the control pressure of z. B. 45 bar, the flow indicator 51 can thus control a subsequent function in a machine tool. At the time t ₁ , the main stage 33 of the pressure reducing valve 34 is still open, since the clamping pressure p ₂ which is higher by the pressure difference Δ p has not yet been reached. Further, at time t _1, the differential pressure valve 45 closed ge because the Doomed from the second orifice 47 gently pressure gradient is smaller than the pressure difference at the valve 45 set pressure difference, which z. B. 5 bar can carry.

The pressure in the cylinder chamber 25 can thus continue to increase along the straight lines 52 until it reaches the clamping pressure p ₁ at the time t ₂ . The clamping pressure p ₂ is greater than the control pressure p ₁ by the pressure difference set on the pressure differential valve 45 , so that when it reaches or exceeds the pressure differential valve 45 also opens and an additional control oil stream flows via the control throttle 42 in parallel to the control oil flow via the second control line 46 , The first control line 36 , the open pressure valves 45 and 44 to the tank 22 forms. The now on the control throttle 42 training pressure drop acts on the main stage 33 , where goes through the pressure reducing valve 34 in the control position and the clamping pressure in the cylinder chamber 25 to the set value of z. B. limited to 50 bar. The clamping pressure p ₂ thus results from the sum of the set pressures of the pressure limiting valve 44 and pressure differential valve 45 . The clamping pressure can now be adjusted up or down, for which purpose only the setting on the pressure limiting valve 44 has to be changed. Regardless of the adjustment on the pressure relief valve 44 , the pressure difference once set at the pressure difference valve 45 remains constant. To set the device, it is therefore sufficient if only a single adjusting element, namely that on the pressure limiting valve 44 , is actuated. Even after reaching the clamping pressure, the flow indicator 51 continues to signal that the control pressure is not below.

If the clamping pressure along the straight line 53 according to FIG. 2 now falls at time t ₃ , the pressure reducing valve til 34 initially ends its pressure control function and opens while the pressure differential valve 45 closes and interrupts a control oil flow via the control throttle 42 . Thus, only control oil can flow through the second control line 46 and the open pressure relief valve 44 to the tank 22 , where a sufficient pressure in the cylinder chamber 25 is still signaled by the flow indicator 51 . The pressure in the cylinder chamber 25 by the line 53 decreases further, and un he terschreitet at the time t ₄ the control pressure p _1, so also includes the pressure relief valve 44 and the Strö mung indicator 51 outputs the signal, that the control pressure has been exceeded in the cylinder chamber 25 so that the machine is switched off. In the range of the pressure difference between the pressures p ₁ and p ₂ , the valve arrangement 10 can thus process pressure fluctuations in the hydraulics and thus prevent the machine from being switched off prematurely.

Fig. 3 shows part of a second Ventilanord voltage 60 , which differs from that of FIG. 1 mainly by another pilot unit 61 min a double pressure relief valve 62 . For the rest, who provided the same components as in Fig. 1 with the same reference numerals.

The double pressure relief valve 62 , which now forms the two pressure control devices together with the pressure difference valve 45 , has two control connections, of which a first ( 63 ) is connected to the first control line 36 , while the second control line 46 is routed via the second control connection 64 is, so that the second control line 46 no longer opens upstream of the double pressure relief valve 62 , son downstream of it into the first control line 36 . A spool 65 of the double pressure limiting valve 62 is only acted upon by the pressure in the second control line 46 . In addition, the orifice 48 is located downstream from the double pressure relief valve 62 in the two-th control line 46 alone, thus upstream from the merging of the two control lines 36 and 46 .

The simplified double pressure relief valve 62 shown in Fig. 3 is shown in Fig. 4 in a more constructive design in a longitudinal section. As can be seen from FIG. 4, the double pressure limiting valve 62 has a single control slide 65 which is connected in both control connections 63 and 64 . For this purpose, the control slide 65 has a first control edge 66 and a second control edge 67 , which operate simultaneously and in the same direction with an opening movement of the control slide 65 . The spool 65 is acted upon on one end face by the pressure in the second control line 46 in the area between the shuttle valve 38 and the double pressure relief valve 62 , while on its other end face an actuating device 68 of any design applies an adjustable counterforce.

The operation of the second control device 60 is basically the same as that of the first Steuerein device 10 , as with the help of the double pressure relief valve 62, the control pressure p ₁ and with the pressure difference valve 45, the pressure difference Δp is adjustable, while the clamping pressure p ₂ from the Sum of the setting of both pressure valves 62 and 45 results. In contrast to FIG. 1, in the second valve arrangement 60, the two control oil flows are passed separately via the control lines 36 and 46 via the double pressure limiting valve 62 . The opening pressure for the double pressure relief valve 62 is the same for both control connections 62 and 64 . The partial flow flowing through the second control line 46 , in which the orifice 48 is also connected, is decisive for monitoring the control pressure in the cylinder chamber 25 . The pressure drop of the orifice 48 thus no longer has any influence on the other partial flow via the first control line 36 , which is primarily decisive for the control function of the pressure reducing valve 34 . Through this separation of the control oil flows, the pressure reducing valve 34 can be set to a relatively low clamping pressure and the pressure difference Δp can be kept small, so that, for. B. Pressure differences from 2 to 10 bar are adjustable. In addition, the pre-control unit 61 allows an energy-saving mode of operation.

Fig. 5 shows part of a third Ventilanord voltage 70 , which differs from the second valve assembly 60 of FIG. 3 mainly in that it has another pilot control unit 71 and a separate pressure differential valve in the first control line 36 ent falls. Otherwise, the same components as in FIG. 3 or FIG. 4 are provided with the same reference symbols.

In the pilot control unit 71 , its two pressure control devices are integrated in the double pressure relief valve 62 ; characterized the double pressure relief valve differs 62 opposite that in which the control edges 66 and 67 are off in the pre control unit 61 by only one other control slide valve 72, formed so that the second control edge 67 72 the second control connection during an opening movement of the valve spool 64 controls before the first control connection 63 . It is thereby achieved that, upon reaching the control pressure p _1, a control oil stream via the second control connection 64 to the drain tank can, thus, the flow indicator 51 indicates the attainment of the control pressure. The first control connection 63 is still blocked in the area between the times t ₁ and t ₂ , as a result of which the pressure reducing valve 34 cannot yet go into its control position. Only at a further opening stroke of the spool 72 corresponding to the pressure difference Δp also opens the first control edge 66 and the pressure reducing valve 34 limits the clamping pressure at the height p ₂ .

The third valve arrangement 70 is relatively simple and cheap to build due to the elimination of the pressure difference valve. The control pressure p ₁ and the clamping pressure p ₂ are still adjustable by adjusting the actuating device on the double pressure relief valve 62 . The pressure difference ∆p is no longer adjustable at the pressure relief valve, but results from the installation of springs of different stiffness at the double pressure relief valve 62 .

Fig. 6 shows a fourth valve assembly 80 in a simple representation, which differs from the first valve assembly 10 of FIG. 1 as follows, where the same reference numerals are used for the same parts.

In the fourth valve arrangement 80 , the main stage 33 of the pressure reducing valve 34 is configured in a three-way function. In the pilot control unit 43 , a proportional solenoid 81 is used to adjust the pressure limiting valve 44 , which in a manner known per se loads the force-transmitting spring 82 accordingly. When the proportional magnet 81 is not energized, the spring 82 is tensioned, so that the pressure relief valve 44 is set to its lowest value. With the armature of the proportional magnet 81 , a switching element 83 is now coupled, which is pressed by the spring 82 into a locking position 84 when the magnet 81 is not energized. When the magnet 81 is excited, the switching element 83 assumes a through position 85 . The control line 36 is now routed downstream from the pressure relief valve 44 via the switching element 83 and further via the flow indicator 51 to the tank 22 . The pressure limiting valve 44 and the switching element 83 form the two pressure control devices of the pilot control unit 43 .

The mode of operation of the fourth valve arrangement 80 corresponds largely to that of the first valve arrangement 10 , but a safety function is additionally achieved by the switching element 83 coupled to the proportional magnet 81 . If the electric current to the proportional solenoid 81, so the force and the spring 82 is lowered presses the movable armature of the propor tionalmagnet 81 and thus also the switching member 83 into the illustrated locking position 84, so that the control line is interrupted 36th This increases the pressure in the cylinder chamber 25 to the value of the system pressure relief valve and the clamping pressure in the clamping cylinder 13 cannot collapse in the event of a power failure. It is assumed that the setpoint zero, ie the lowest setting pressure, releases a minimum current to the magnet 81 , so that the through position 85 of the switching element 83 is reached.

Of course, changes are possible to the valve arrangements shown without departing from the spirit of the invention. The adjustment on the pressure relief valve can be made in any way and is not limited to an actuator with a proportional solenoid. The clamping pressure can also be set manually using a handwheel, hydraulically or electrically using an electric motor. When using an electric motor, especially in conjunction with a worm gear to adjust the clamping pressure, the opening pressure cannot change in the event of a power failure. Of course, a proportional solenoid adjustment can also be used to adjust the pressure valves, which works with a reverse operating principle, whereby an associated valve cone is pressed by its spring with maximum force onto the valve seat and an increasing control voltage in the proportional solenoid increasingly relieves the valve cone and thereby causing a sin opening pressure. With such a proportional magnet adjustment, a power failure leads to a maximum clamping force in the clamping cylinder. The valve assemblies can be designed as an intermediate plate device under a directional control valve or as independent devices in plate assembly or pipe connection technology. The safety function shown in FIG. 6 can also be applied to the double pressure relief valves according to FIGS. 3 and 5. The same effect can be achieved if the shut-off function performed by the switching element 83 against the control line is integrated upstream of the pressure relief valve. Instead of the pressure differential valve shown in Fig. 1, a check valve with adjustable spring preload can of course also be used. The pressure reducing valve can be designed as a 2-way as well as a 3-way valve.

Claims (9)

1. Valve arrangement for controlling and monitoring the working pressure of a hydraulic consumer, for. B. the chuck of a machine tool with a consumer upstream pressure reducing valve, which is pilot-controlled by a pilot valve determining the working pressure, for which purpose a control line is led from a consumer connection via a control throttle and the pilot valve to the tank and in which the pressure drop caused by the control throttle against Force of a spring can act on a control element of the pressure reducing valve, and with a flow indicator connected downstream of the pilot valve, characterized in that a parallel, second control line ( 46 ) branches off from the control line ( 36 ) upstream of the control throttle ( 42 ) and to the pilot unit ( 43 ; 61 ; 71 ), in which two pressure control devices ( 45 , 44 ; 45 , 62 ; 44 , 83 ) are arranged so that a control pressure (p.) Lower by a predetermined pressure difference (Δp) compared to a clamping pressure (p ₂ ) ₁ ) is adjustable. 2. Valve arrangement according to claim 1, characterized in that the pilot control unit ( 43 ) consists of a pressure limiting valve ( 44 ) determining the clamping pressure and a pressure differential valve ( 45 ) determining the pressure difference (Δp), which the pressure limiting valve ( 44 ) in the first control line ( 36 ) is connected in series and that the second control line ( 46 ) runs parallel to the pressure difference valve ( 45 ) and is connected to the inlet of the pressure relief valve ( 44 ). 3. Valve arrangement according to claim 2, characterized in that in the second control line ( 46 ) the pressure relief valve ( 44 ) is preceded by a second throttle point ( 47 ). 4. Valve arrangement according to claim 1, characterized in that the pilot unit ( 61 ) consists of a double pressure relief valve ( 62 ) and a Druckdifferenzven valve ( 45 ), the latter in the first control line ( 36 ) of a first control connection ( 63 ) the double pressure relief valve ( 62 ) is connected upstream, while the second control line ( 46 ) can be controlled by a second control connection ( 64 ), and that both control connections ( 63 , 64 ) of the double pressure relief valve ( 62 ) are controlled simultaneously and in the same direction will. 5. Valve arrangement according to claim 4, characterized in that the second throttle point ( 47 ) of the second control connection ( 64 ) is connected upstream. 6. Valve arrangement according to claim 1, characterized in that the pilot unit ( 70 ) consists of a double pressure relief valve ( 62 ) which the control pressure assigned to the second control connection ( 64 ) before the first, the clamping pressure associated Steuerver connection ( 63 ) controls and thus the pressure difference (Δp) is determined by the rigidity of the associated spring and that the second throttle point ( 47 ) is connected upstream of the second control connection ( 64 ). 7. Valve arrangement according to one of claims 4 to 6, characterized in that one of the flow indicator ( 51 ) associated diaphragm ( 48 ) is only switched into the control oil flow flowing via the second control connection ( 64 ). 8. Valve arrangement according to one or more of claims 1 to 7, with a pressure-actuated valve actuated by a proportional magnet, the closing member of which can be loaded on the one hand by the pressure to be regulated and on the other hand by a spring, the pretension of which is variable by the proportional magnet, characterized in that that the armature of the proportional magnet ( 81 ) is positively connected to egg nem switching element ( 83 ) which is connected to the control line ( 36 ) and which gneten ( 81 ) blocks the control oil flow ( 84 ) when the magnet is not energized ( 84 ) and when the magnet is energized ( 81 ) a through position ( 85 ) takes. 9. Valve arrangement according to claim 8, characterized in that the switching element ( 83 ) is connected downstream of the pressure relief valve ( 44 ).